WASHINGTON — Federal bank regulators are scrutinizing more than 150 home loan-related lawsuits directed at lenders and mortgage companies, a top official at the Federal Deposit Insurance Corporation plans to say Thursday, underscoring the threat the largest U.S. banks face from faulty and improper mortgage and foreclosure practices.

The revelation will likely add to large banks’ woes, as the five biggest servicers — Bank of America, JPMorgan Chase, Wells Fargo, Citigroup and Ally Financial — currently face up to $30 billion in penalties from state attorneys general and federal agencies for wrongful foreclosures and other mortgage-related misdeeds.